US2423336A - Radio controlled pilot system - Google Patents

Description

y .1947. F. L. MOSELEY 2,423,336

RADIO CONTROLLED PILOT SYSTEI Filed Feb; 10, 1941 4 Sheefs-Sheet 1 F. L. MOSELEY RADIO CONTROLLED PILOT SYSTEI July 1, 1947,

4 sheets-sheet 2 Filed Feb. 10, 1941 522mg W y 1947- F. L. MOSELEY 2, 23,336

RADIO CONTROLLED PILOT SYS'I'EI Filed Feb. 10, 1941 4 Sheets-Sheet 3 3 v wwwbot Ma-SA. fi/aaelqy,

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July 1, 1947. MOSELEY, 2,423,336

RADIO CONTROLLED PILOT SYSTEII Filed Feb. 10, 1941 4 Sheets-Sheet 4 PIT/l Patented July 1, 1947 UNITED STATES PATENT OFFICE RADIO CONTROLLED PILOT SYSTEM Francis L. Moaeley, Chevy Chase, Md. aaalgnor t 8mm Gm Company. Inc. Brooklyn, N. Y., a corporation of New York Application February 10, 1941, Serial No. 378,296

:2 Claims. (Cl. 244-") The present invention relates to the automatic control of aircraft, and particularly to the control of aircraft by signals received from suitable remote radio stations located on the ground.

It has heretofore been proposed to utilise positional signals transmitted by radio statims for operating a position indicator located in an aircraft to give a pilot a visual indication of his position. Such signals are produced at the presout time by means of doubly modulated transmitters which define a plane of equal modulation. It is also known to utilize a radio transmitter provided with a suitable antenna setting up a radiation pattern having a constant potential along a line suitable for employment as a glide path registering through an indicator to guide a pilot in the landing of the aircraft. It has further been proposed to employ a receiving loop stabilized in azimuth on the aircraft to define a course relative to a non-directional transmitter.

Any of the above or other radio transmission systems in conjunction with suitable receivers, registering in the aircraft signals varying with the position of the aircraft in space, is suitable for use in connection with the invention. I

employ the positional data derived from the radio signals to steer the aircraft automatically, without the agency of the pilot, on a flight path coincident with the predetermined radio-defined course. The invention automatically corrects departures of the aircraft from the predetermined course by suitably correcting the direction of the aircraft for returning the aircraft to the course.

It will therefore be understood that the primary object of this invention is to automatically steer an aircraft on a flight path coincident with a predetermined course defined by positional radio signals.

A further object of the invention is to automatically correct departure of the flight path from the radio-defined course by directional corrections of an amount proportional to the departure.

A further object of the invention is to automatically correct lateral departure of the flight path from a radio-defined course by heading corrections of an amount proportional to the departure.

A still further object of the invention is to automatically correct departure of the flight path from a radio-defined course by directional corrections proportional to the rate of change of position relative to the course.

A further object of the invention is to automatically correct lateral departure of the flight 2 path from a radio-defined course by heading corrections of an amount proportional to the rate of change of position relative to the course.

A further object of the invention is to automatically steer an aircraft over a flight path coinciding with a course defined by suitable radio signals and varying in altitude.

Another object of the invention is to automatically correct vertical departure of the flight path from a radio-defined course by elevation control corrections of an amount proportional to the departure.

Another object of the inventionis to automatically correct vertical departure of the flight path from a radio-defined course by elevation control corrections of an amount proportional to the rate of change of position relative to the course.

A further object of the invention is to automatically bring an aircraft into a landing over a flight path coinciding with a course defined by suitable radio signals.

A further object of the invention is to automatically steer an aircraft through radio responsive control means operating automatic pilot means in the aircraft.

A further object of the invention is to operate an aircraft steering control by an actuating motor in a proportionate manner without overrunning.

A still further object of theinvention is to 0perate aircraft heading and elevational controls by actuating motors in a proportionate manner without overrunning.

In carrying out these objects I provide a motor for controlling the direction of the aircraft. This motor is controlled by a positional signal obtained from a radio receiver which varies in amplitude according to the amount of departure of the aircraft from course. Normally this will be a small D. C. voltage, and in my system this positional signal is opposed by a follow-up signal which measures the directional correction through which the aircraft is turned under operation of the motor. When the directional correction is proportional to the departure, the two signals will be equal and opposite and the motor will come to rest.

The positional signal obtained from the radio receiver is of the order of a few microvolts and require great amplification in order to obtain proper actuation of the motor. In order to avoid the diificulties inherent in direct current amplification I convert the D. C. control signals proportional to the departure of the aircraft from course and to the directional correction under operation of the motor to A. C. previous to ampliflcation. If desired, the follow-up signal may be introduced after conversion of the positional signal, in which case it will be supplied as an A. C. voltage inverse in phase to the converted positional signal.

I prefer to employ a two phase alternating current motor in which one field coil is energized by a local A. C. supply. The conversion of the D. C. signals to A. C. is carried out under control of the A. C. supply so that the amplified signal will have the same frequency as the A. C. supply, and I provide means for causing the amplified signal to lead or lag the A. C. supply by 90. The amplifled signal is supplied to the other field coil of the motor. The phase inversion of the amplified signal is dependent upon the polarity of the original D. C. signal and will operate to control the direction of the motor.

As used in connection with a doubly modulated transmission system, the radio receiver output is constituted by two alternating current signals of diflerent frequencies. These signals are separately rectified and the resulting D. C. potentials bucked against each other to produce a resultant D. C. signal proportional to the difference between the original A. C. signals. I

Control systems operating as described may be employed for correcting lateral departures of the aircraft from a course by controlling the heading, and for correcting vertical departures from course by controlling the angle of climb or descent particularly for landing operations. According to the invention a complete system will preferably be provided for controlling the aircraft both horizontally and vertically.

The invention also contemplates automatically controlling the bank of the aircraft in dependency on the rate of turn.

In the specific embodiment to be described the heading and elevation control systems are separately responsive to different radio signals but under certain conditions where the aircraft is driven off course both horizontally and vertically may simultaneously operate to return the aircraft to course.

The inventive system will most conveniently be operated in conjunction with, and through the agency of, a suitable automatic pilot. Ordinarily such automatic pilot will be of the gyroscopic type and the radio responsive control motor may perform its function of correcting the direction of flight through one or more of the direction setting controls of the automatic pilot.

The operating principles of the invention, in regard to the horizontal control of the direction, are broadly applicable to dirigible craft, such as surface craft.

This invention will be further understood in reference to the drawings in which:

Fig. 1 illustrates the flight path of aircraft under my steering control device;

Fig. 2 represents a block diagram showing my invention applied to obtain complete automatic three-dimensional steering control of an aircraft;

Fig. 3 is a circuit diagram of my control device for the turn and bank controls of an aircraft;

Fig. 4 represents the signal and power supply circuits for the operating units shown in Fig. 3;

Fig. 5 is a circuit diagram of my elevator control device;

Fig. 6 represents the signal supply circuit of the operating unit shown in Fig. 5; and,

Fig. '7 is a diagrammatic representation of the operating relationship between an automatic pilot and the control surfaces of an aircraft.

As shown in Fig. 1, the line AB represents in a horizontal planea course defined by positional radio signals. This course is produced in a known manner by the employment of doubly modulated radio transmitters to form radiation fields I and 2 of differing modulation frequencies. At the present time modulated frequencies of and cycles are employed. The two radiation fields define a vertical plane represented as course AB in which the field strength of the two radiation fields are equal. By suitable circuits responsive selectively to the different modulation frequencies used in connection with a radio receiver on an aircraft, it is possible to obtain a signal varying with the position of the aircraft relative to its departure from course AB.

In order to control the flight path of the aircraft so that it will coincide with the course AB it is necessary to establish in the aircraft a compass base line parallel in direction to the course AB, and to control the flight path so that its deviation from the established base line heading varies proportionately to the departure from the course. Assuming an arbitrary departure, the flight path of an aircraft controlled in this manner is represented by the path CD, in which the arrows represent the heading of the aircraft as it passes over the flight path. It will be noted that the heading deviation is large under large departure, and becomes progressively smaller as the flight path approaches the course. The amount of correction in heading may be such as is required under operating conditions, and manifestly the proportionality need not be linear.

It has been found desirable in order to avoid hunting of the aircraft about the course to provide a further control of the aircraft heading proportionate to its rate of change of position relative to the course. When this is applied in controlling the heading corrections of the plane in addition to the correction proportional to the departure itself, the flight path of the aircraft under control of my invention is represented by a path E! of Fig. 1. It will be noted that because of the velocity of the aircraft in its return to the course it has been caused to assume a heading parallel to the course just previous to reaching the same. This permits the aircraft to attain an exact "on course" position through its crosswise momentum, so that the aircraft does not overshoot the course. It will be noted that in the flight path CD the aircraft reached its on course" position with a slight cross-course velocity which would cause the flight path to overshoot the course by a slight amount. Whereas the departure resulting from overshooting the course would be immediately corrected, the necessity for this is avoided by employing a control responsive to the rate of change of the departure.

By utilizing a steering control responsive to the rate of change of departure, it is also possible to obtain an accelerated correction of heading when the aircraft suddenly departs from course because of conditions encountered in flight. Because of the relatively large heading correction in response to a quick departure, the amount of the departure is therefore minimized.

It will be understood that under operating circumstances wherein the flight path includes a drift component transverse to the direction of the aircraft caused by side winds, the direction of flight of the aircraft cannot be directly controlled itself because the drift component depends on the magnitude of side winds which are not accurately determinable. The flight path, however, is variable in dependency on the change of direction Masses of the aircraft and consequently the desired iiis'ht path may in be attained through the described directional corrections turning the aircrafttowardcourse. Therateof approach tothe couraedependsontheanglethroughwhichthe aircraft is turned, toward course. and therefore willlikewiseva yinproportiontothe extentof departure. The control means operating proportionallytothedepartureandtotherateofchange of departure operates to compensate for drift by increasing the directional correction of the aircraftinprop rtiontoitsvelocityofdriftwhen suehdriftopposesitsreturntocourse, anddecreases the directional correction when the drift is toward course, thereby substantially maintaining the desired direction of flight and ground course. 1

It will further be understood that the above principles of operation may be carried out with any suitable source of positional signal for the aircraft and are in no way dependent on the specine radio system described. The same principles apply to the control of an aircraft in a vertical plane in relation to a suitably arranged source of positional signals defining the desired course in respec to altitude. As a source of such a positional signal it is well known to employ either a transmitter setting up a radiation field having the desired course defined by a path of constant potential, or to use a doubly modulated system operating to define a positional signal varying with altitude. The directional corrections are applied in the vertical plane to return the aircraft to course.

The manner in which my invention functions to carry out the proper steering control procedure to maintain the fiight path in coincidence with the daired course may be described in connection with Fig. 2. As shown therein, radio range receiver t is provided with antenna 6 for receiving the doubly modulated radiation field described above. This receiving system is well known, being utilized to operate the vertical needle of the crosspointer instrument I for the purpose of giving the pilot a visual indication of his position relative to the course. The output of the range receiver is utilized to operate the heading control motor 8. This motor controls the direction of the aircraft in a horizontal plane through operation of the rudder. To obtain the desired actuation of the rudder under control of motor 8 I contemplate the use of an automatic pilot in the aircraft, one such pilot being disclosed in Patent No. 1,992,970 of March 5, 1935, for Hydropneumatic automatic pilot.

This type of automatic pilot is well known in the art, but its operation is diagrammatically illustmied in Fig. 'l. The function of the automatic pilot in normal operation is to maintain the orientation of the aircraft constant in space. This is accomplished under control of suitable gyroscopes described in the above noted patent which actuate through servo-operated motors the control surfaces of the aircraft. Thus, as shown in Fig. 'l, rudder 9 is operated by motor ill under fluid pressure received from oil pressure lines ii. In order to obtain proportionate operation of the rudder by the gyroscopic control mechanism, a follow-up connection i2 is also employed. Similarly, ailerons I3 are operated by motor I with oil pressure lines I and follow-up connection I 6. Elevators i! are similarly operated by motor is provided with oil pressure lines I! and follow-up connection". The operating mechanism is described in detail in Patent No. 1,992,970.

Theautomaticpilotthusoperatestocontrolthe orientation of the aircraft about the three principal axes simultaneousb. llanual control means are normally provided for selecting the desired direction settings. Thus, heading control knob fl is provided for the directional gyropilot unit 22 andisoperativetovarytheheadingoftheaircraft under the operation of the mic control mechanism. Similarly. bank control knob 23 of gyropilot It is operative to select the desired angle of bank for the aircraft through operation of the ailerons II, and elevator control knob 2| is provided to select the desired angle of climb or descent of the aircraft.

As shown in Pig. 2, motor 0 is provided with reduction gearing It and is operatively connected to the heading control 2|. so as to control the heading of the aircraft through the desired operation of the rudder. In order to obtain a sumcient output to operate the turn control motor I, I provide turn control amplifier 21 for amplifying the output of the radio range receiver.

In order to obtain a heading correction proportional to the departure of the aircraft, it is necessary to proportion the operation of the turn control motor I to the amplitude of the positional signal from the radio range receiver. For this purpou it is convenient to employ a potentiometer 18 in the circuit shown with battery 29, adiustable resistance and center tapped resistance 3|. As shown. this potentiometer is operatively connected to turn motor I and functions to supply the turn control amplifier with a voltage proportional to the heading correction bucking the positional signal from the radio receiver. Under control of this circuit turn motor 8 operates to change the heading of the aircraft only 'until the follow-up bucking voltage becomes equal and opposite to the positional signal, and thereby effects a heading correction proportional to the departure.

Although my turn control mechanism would operate in itself to return the aircraft to the vertical plane of the desired course, better control is obtained by effecting rigid turns free from skid by banking the aircraft in proportionto the rate of turn. For this purpose bank control-motor 32 is provided, and is operatively connected through gearing 33 to the bank control of the automatic pilot. In order to obtain bank in proportion to the rate of turn I provide a'rate of turn measuring device It responsive to the speed of turn control motor 8. The output from the rate of turn measuring device is amplified in the bank control amplifier 35 to operate bank control motor 32. In order to obtain bank proportional to the rate of turn, it is necessary that the operation of bank control motor 32 be proportional to the rate of turn signal, and for this purpose I provide a potentiometer 35 similar in function to potentiometer 28. Potentiometer 36 is operatively connected to bank control motor 32 and supplies a follow-up signal proportional to the angle of bank bucking the rate of turn signal. The amplitude of the follow-up voltage increases in proportion to the operation of bank control motor 32 and therefore causes motor 32 to bank the plane proportionately to the rate of turn.

In order to prevent over-running of the bank control motor, and consequent huntin of the aircraft about the correct angle of bank, rate of bank measuring device 31 is provided for measuring the speed of bank control motor 32. The rate of bank signal is introduced into the ba k control amplifier to produce a positive braking action on bank control motor 32 as the inp t 818- nal, determined by thecombined rate of turn signal and bank control follow-up voltage, approaches zero. Through this mean any tendency of the bank control motor to overrun the correct setting is automatically checked and hunting is avoided. 1

In order to obtain automatic control of the aircraft in a vertical plane a glide path receiver 30 with antenna 30 is utilized. As is well known, this receiver supplies a positional signal for operating the horizontal needle of the cross-pointer instrument 1 in order to give the pilot a visual.

indication of his departure from course in altitude. I employ this signal to control the altitude of the aircraft by the operation of motor 40. Although the altitude control could be obtained through throttle operation, I prefer to use motor 40 to operate the elevator control 25 of the automatic pilot. For this purpose, motor 40 is provided with reduction gearing II and is operatively connected to the elevator control 25. Motor 40 is operated from the output of the glide path receiver 38 through elevator control amplifier 38.

In order to obtain a correction proportional to the departure in altitude I provide follow-up potentiometer 42 operatively connected to motor 40 for supplying a follow-up voltage proportional to the vertical directional correction bucking the glide path receiver signal 38.

For the purpose of preventing overrunning of motor 40 and consequent hunting of the aircraft, I provide speed measuring device 43 to obtain a signal proportional to the speed of motor 40 which is introduced into the elevator control amplifier 38 so as to produce a positive braking action of elevator control motor 40 as the input signal from the combined glide path receiver signal and the follow-up voltage approaches zero.

In each case the steering motor is controlled by a signal measuring the displacement from the desired direction, and by a follow-up signal measuring the amount of directional correction as the orientation of the aircraft is changed by operation of the motor. When the correction is of an amount proportional to the deviation to be corrected the signals are equal and opposite, and no further operation of the steering motor occurs until a further deviation takes place. Where desirable to prevent overrunning of the motor, its speed is measured, and if it is moving when the control signal and follow-up signal are equal, the speed signal positively brakes the motor to a stop.

In order to measure the rate of departure from course a circuit component may be employed which is responsive to the rate of change of the positional signal and operates to superimpose on the signal a component proportional to its rate of change. Such a device is diagrammatically illustrated at 44 for the heading control and at I! for the elevator control. When the rate of change measuring circuit is employed, the directional corrections will be accelerated and increased in proportion to the rate of change of departure to prevent overshooting on return to course and to minimize departure.

It should be mentioned that the operation of the invention has been described in combination with commercially conventional receivers and fiight control instruments. These operating units are available for my purposes in existing aircraft at th present time, and in such instances may be economically employed therewith, but it 8 is clear that the operating principles of my system are independent of the particular units de- Turn control circuit The control circuits for the turn control motor are shown in Figs. 3 and 4. In Fig. 4 is diagrammatically illustrated radio range receiver 5 which is responsive to the doubly modulated radiation field illustrated in Fig. 1. The radio range receiver separates the two modulating frequencies and provides a dual output. The output signals constitute alternating currents of the respective modulations of the field pattern, and are proportional to their respective amplitudes at the loca tion of the aircraft in space. The output signals are amplified by tuned amplifiers I and II which are coupled to a rectifier network 50 by transformers 48 and 59. M is well known, the rectifier network produces a direct current signal proportional to the relative strengths of the mod lation frequencies of the field pattern, varying .in sign in dependency on which modulating frequency predominates, and falling to zero where the field strengths are equal. In this way a sigmanner, and in my system is utilized to provide the basic control for the turn motor I. For this purpose. the signal from the rectifier network 50 is led to terminals 5| which are connectable with the signal input terminals 52 of the turn control amplifier as shown in Fig. 3. Low pass filter III is provided to remove residual components of the modulating frequencies which may be transmitted through the rectifier network.

As shown in Fig. 4 I also provide a power supply for the turn control motor comprising vibrator 53, transformer 54 and rectifier II. This supplies an alternating current output to terminals 56, and, through choke coils 51 and condensers 58, direct current at terminals 59 and I.

The alternating current supply from terminals '58 is connected to terminals SI of the turn control amplifier, and the direct current from terminal ill is connected to terminal 82. The power supply and amplifier are provided with a common ground circuit.

The turn signals from terminals I! are connected through switch I to conductors N and II. Conductor 84 is connected to conductor '0 through center tapped resistance ii and potentiometer 28, the operation of which will be hereinafter described. Conductors 6! and 86 are connected to terminals '1 and 68 of vibrator II. This vibrator comprises contact points II and H, and vibrating blade 12 which is actuated by magnet coil 18. The output from the vibrator is fed to the center tapp d Primary ll of transformer II. The magnet coil of the vibrator is connected to the alternating current source through conductors II and TI and half-wave rectifier ll. Consequently vibrator blade 12 is actuated by the resulting current pulses to produce an alternating current in transformer II of a frequency equal to the alternating current supply, and of an amplitude proportional to the direct current input to the vibrator. The vibrator constitutes in efiect a modulator.

Transformer 1! is provided with secondary II masses 9 which is connected to control grid 88 of the first turn amplifier tube 8|. Condenser 82 is placed across the secondary of transformer 18 to improve the waveform of the alternating current generated by the vibrator.

The turn control amplifier constitutes a conventional system employing, in addition to the input tube 8|, resistance coupled tubes 88 and 88 which feed through transformer 88 push-pull tubes 88 and 81. Tubes 88 and 81 are connected to the split primary 88 of output transformer 88. Primary 88 is shunted by condenser 88 to provide further improvement in the waveform.

The secondary ll of transformer 88 couples the amplifier output to field coil 92 of the turn control motor 8.

Turn control motor 8 is also provided with field coil 88 which is fed through conductors 84 and 88 by the alternating current supply.

As shown, motor 8 constitutes a two-phase motor which is operated by the alternating current source and the alternating current gener-' ated by the vibrator from the direct current positional signal. It will be understood that due to the dependency of the actuating coil of the vibrator on the alternating current supply, the alternating current generated by the vibrator maintains a definite phase relation with the alternating current supply. It will also be understood that the alternating current generated by the vibrator will shift its phase by 180 in response to a reversal of direction of the direct current signal. The circuit constants of the turn control amplifier are so adjusted that the output thereof as nearly as possible leads or lags the alternating current by 90. Consequently, motor 8 will operate in dependency on the direct ourrent input to the vibrator, and will respond to a reversal in polarity thereof by a reversal in its direction of rotation. Y

Turn motor 8 is operatively connected to the heading control of the automatic pilot, as described in connection with Fig. 2. The operation of the heading control causes a heading variation of the aircraft which is directly proportional to the movement of the heading control.

Operation of the turn motor 8 actuates potentiometer 28 to set up a voltage between conductors 88 and 68 as the contact arm moves relative to the midpoint of the resistance element. The potentiometer is supplied with the desired voltage gradient by means of battery 29 and rheostat 88. The voltage set up by the potentiometer is in direct proportion to the actuation of the heading control, and consequently this voltage is a measure of the deviation in heading caused by operation of turn motor 8. It will therefore be understood that operation of turn motor 8 is inaugurated on the appearance of a positional signal at terminals 52 indicating a lateral departure of the aircraft from its course, and that the turn motor continues to operate to change the heading for returning the aircraft to course until the voltage set up by potentiometer 28 balances out the positional signal, that is, until the heading corretion as measured by this voltage is equal to the departure as measured by the positional signal voltage at terminals 52. In this way the followup voltage fromthe potentiometer acts to proportion the heading correction of the aircraft to its departure from course, and thereby causes the aircraft to correct its departures by a flight path such as shown at CD in Fig.1. The flight path for correcting departure is under control of the output from potentiometer 28 which is determined by the input voltage supplied thereto, and by the type of winding, which may be linear or non-linear as required. It will be understod that the heading correction is continuously diminished as the aircraft approaches course in accordance with the diminishing position signal at terminals 82.

Manual control of the aircraft may be obtained through my device by operation of switch 88 to interconnect conductors 84 and 88, whereupon the control signal for the turn control motor is obtained from the follow-up potentiometer 28. The motor therefore runs to restore the system to balance and in so doing changes the heading of the aircraft.

To employ this action control knob I" is provided connected to potentiometer 28 by gearing "8. Operation of knob I'll rotates potentiometer 28 relative to turn motor 8 by slipp of friction clutch I15. Motor 8 immediately responds to the output from the potentiometer circuit resulting from movement of the potentiometer from balance position, and operates to change the heading until the potentiometer is returned to balance.

The amount of heading change under manual control will be proportional to the rotation given control knob I11, and consequently the settin of the automatic pilot may be controlled hereby. This is particularly useful when employed in connection with the automatic bank control to be described below.

In order to obtain a heading correction proportional to the rate at which the aircraft is approaching or leaving the course, I may employ circuit means responsive to the rate of change of the positional signal. As shown in Fig. 4, these may comprise an inductance 88 shunting the receiver output, and resistor 8'I and condenser 88 which are in parallel to each other and in series with the receiver output. If the direct current signal increases from a steady state the reactance temporarily assumes a high resistance to the increasing current and therefore increases the output voltage proportionately beyond what it would be in the steady state. Simultaneously condenser 88 effectively shunts resistor 81 for the rising current and additionally increases the output to terminals ii. In effect, therefore, the rate responsive circuit superimposes on the receiver output a signal component proportional to its rate of change, and thereby increases the heading correction. i

Similarly, in response to movement of the aircraft toward course the receiver output drops, and inductance 96 generates a self-induced current of reverse polarity which further reduces the voltage at terminals 5|. At the same time a decreasing voltage is set up over resistance 81 and condenser 88 immediately producing a voltage further opposing the receiver output. In this way, a component proportional to the rate of decrease of the positional signal is superimposed thereupon, and the heading correction of the aircraft is decreased in dependency on the rate of approach to course.

In the input circuit shown, a the follow-up potentiometer and the positional signal source are in series, the rate responsive circuit components also superimpose a component on the circuit proportional to the rate of change of the potentiometer output.

The turn control motor operates under the basic control of a positional signal proportional to departure from course. The basic signal is trans- 11 formed to an alternating current having the irequency of a locally generated A. 0. supply, is ampliiied, and is utilized with the locally generated A. C. supply to actuate the turn control motor. The change oi heading oi the aircraft under operation of the turn control motor is also measured by a follow-up signal which opposes the positional signal. In the iorm shown the iollow-up sllnal is constituted by a D. C. voltage opposing a D. C. positional signal, and the polarity of the resulting voltage determines whether the amplified A C. signal leads or lags the local generated A. 0. pp y.

In the embodiment shown wherein the positional signal is derived from a doubly modulated radiation system it first appears as two alternating currents oi. different frequencies which are transformed to an alternating current of the frequency of the locally generated A. C. supply through rectification to a single direct current signal which is then converted to A. C. under control of the locally generated A. C. supply.

Circuit components have also been shown for superimposing on the positional signal a component proportional to its rate of change.

Bank control circuit It is desirable, in order to avoid side-slip oi the aircraft, to bank the same in proportion to the rate of turn. It will be understood that under operation of the automatic pilot heading control the heading is changed by a constant amount for each revolution of turn motor 8. In order to determine the rate of turn of the aircrait it is therefore convenient to measure the speed oi turn control motor 8, and to bank the plane in proportion to this speed.

For this purpose I provide an inductance-resistance bridge comprising ileld coil 02 oi the turn motor 8, and resistance I02 as one pair of arms, and inductance 99 and resistances I and IM as the other pair. This bridge is balanced by rotating the motor manually to provide an input voltage for the turn control amplifier through operation of potentiometer 28, and the motor is then blocked in this position. The total value of resistances I00 and MI is then adjusted until the phase angle of the voltage drop across these resistances is the same as the drop across resistance I02. The relative values oi resistances I00 and NI are then adjusted without changing their total value so that the voltage drop across resistance I M is exactly equal and opposite to that developed across resistance I02. When the turn motor 8 is allowed to rotate, the inductance of field coil 92 will increase proportionately to the rotation, and an unbalance voltage proportional to its speed will be supplied to conductors I03 and I04. This speed signal will be oi a irequency equal to the alternating current supply, of an amplitudeiproportional to the speed oi turn control motor 8, and will reverse its phase through 180 in dependency on reversal oi turn motor 8. The speed signal constitutes a basic control for bank motor 32 which is operatively connected to the bank control of the automatic pilot and which thereby varies the bank oi the aircraft.

The output of the turn motor speed bridge is connected in series with potentiometer 30 which receives an alternating current supply through conductors I05 and I08. The potentiometer II is shunted by center tapped resistor I01. Potentiometer 36 supplies an alternating iollow-up signal of an amplitude proportional to the displacement of the potentiometer irom its center position and undergoing a phase reversal oi 180 as the potentiometer arm passes irom one side to the other side oi the center position. 0onsequently. the output oi iollow-up potentiometer It may be caused to oppose the output irom the turn motor speed bridge by suitable phase shiiting means inserted in its supply circuit. For this purpose I provide condenser I and inductance I00.

In order to prevent overrunning oi the bank control motor I! I provide means ior measuring its speed, which becomes operative to supply an input control voltage ior the bank motor to brake it, should it overrun the primary control signals constituted by the voltages irom the turn control motor speed measuring device and the bank motor iollow-up potentiometer. This is constituted by a speed responsive resistance-inductance bridge comprising ileld coil II! oi the bank control motor 32, inductance III, resistance III, and resistances III and Ill. The output of this bridge and its operation provide a signal measuring the speed oi the bank control motor similar to the speed measuring bridge ior turn control motor 8.

The output oi the bank motor speed measuring bridge is also proportional to the rate oi change 01' the output of the bank control motor iollowup potentiometer circuit, and to the rate oi change oi bank caused by operation oi the bank control motor.

The bank control amplifier is constituted by resistance coupled tubes II! and I It, which ieed push-pull tubes Ill and H0. Input transiormer II! is provided for the amplifier, and includes secondary I20 ieeding the grid of the input tube II! and shunted by condenser IZI to improve the A. C. waveiorm. The push-pull output tuba II! and H0 feed center tapped primary I22 oi output transformer III which is shunted by condenser I24 also to improve the A. C. waveiorm. Output transformer I23 is provided with secondary I25 for matching the impedance oi field coil IIO oi the bank control motor. This motor is also provided with field I20 excited by the local A. C. supply through conductors Ill and I28.

The primary I28 oi input transformer II! is included in the bank motor control circuit which comprises the turn control motor speed measuring bridge, the bank control motor iollow-up potentiometer, and the bank control motor speed measuring bridge, all connected in series.

The bank control motor operates under a signal comprised oi a component proportional to the speed of the turn control motor, a component proportional to the bank of the aircrait under operation of the turn control motor and bucking the turn motor speed component, and a third component proportional to the speed oi the bank control motor bucking the resultant of the first two components.

The operation oi the bank control motor speed measuring bridge is best considered in comparison to the operation of the bank control motor without the bridge. In such a circuit the bank control motor would respond to a signal measured by the diiierence in output between the turn control motor speed bridge and the bank control motor follow-up potentiometer. As the resultant signal varies the bank control motor would tend to overrun as balance is reached, due to its momentum. Overrunning is particularly objectionable because it would result in hunting about the proper bank angle a the operation oi the bank control motor carries the bank iollowup potentiometer through the balancing position.

In order to prevent overrunning or the bank control motor through the position of zero signal resulting from the combined outputs of the bank follow-up potentiometer and the turn control motor speed measuring bridge, the bank control motor speed measuring bridge is employed. This produces a signal proportional to the speed of the bank control motor which operates to oppose the signal otherwise supplied to this motor by a potential proportional to the speed of this motor. In case the motor should overrun on a decreasing signal an increased voltage will be supplied from the speed measuring bridge which will additionally oppose the signal otherwise supplied and reduce its effective value. The output from the speed measuring bridge may include a component produced by the back E. M. F. from the bank control motor on overrunning. As the signal otherwise supplied approaches zero, the speed responsive component will, in case of overrunning, assume relatively thereto a large value and may actually exceed the other signal to supply a reverse effective signal which positively brakes the bank control motor. In any case where the speed control motor i moving to produce a signal from the speed bridge circuit, if the signal otherwise supplied is zero, the speed bridge signal will supply a braking E. M. F. through the bank motor amplifier to the bank control motor which immediately arrests its movement. In this way the movement of the bank control motor is immediately arrested when the turn control motor speed measuring bridge and the bank control motor follow-up potentiometer have equal and opposite outputs.

Elevator control circuit The operating circuits for the elevator control motor 40 are shown in Figs. and 6. The operation of this motor is in many respects similar to that of the turn control motor.

The positional information for controlling the vertical flight path component is derived from a glide path receiver 38. As is well known, this receiver is utilized in connection with a radio transmitter having a radiation pattern providing a path of constant intensity along which the aircraft is guided. The course defined by the glide path transmitter i utilized to bring the aircraft into a landing. The glide path transmitter is modulated at an audio frequency.

As is usual, the output from the glide path receiver is rectified and operates the horizontal needle of the crosspointer instrument I as shown in Fig. 6. The receiver supplies a small D. C. voltage which is generally dependent upon the altitude of the aircraft. Low pass filter I82 is propath receiver and is shunted by battery I85 and vided to remove frequency component which might interfere with the operation of the elevato control motor. When the aircraft is on the desired course the output of the receiver has a definite value, and when the aircraft departs vertically from the course the receiver output increases or decreases in dependency on themrection of the departure. This output from the glide path receiver is supplied to terminals I 3| and I32 as shown in Fig. 6 which are connectable with the input terminals I 33 and I34 of the elevator control circuit shown in Fig. 5. In order to obtain a positional signal which reverses its sign in dependency on which side of the course the aircraft is, I provide resistance I35 connected to terminal I34, This resistance is in series with the output circuit from the glide rhecstat III. The current from battery Ill is employed to set up a potential over resistance I opposing the output from the glide path receiver so that the efiective input to the elevator control circuit will be zero when the aircraft is on course, and which will change its sign depending upon whether the aircraft is above or below the course.

These circuit components in combination with the glide path receiver supply the elevator control amplifier with a positional signal entirely similar to that supplied the bank control amplifier by the rectified input from the range receiver. The elevator control motor 45 similarly operates potentiometer 42 to supply a follow-up voltage in combination with battery I35, rheostat I39, and center tapped resistor I40. The resultant signal from the combined position signal and follow-up voltage is supplied by conductors I4! and I4! to vibrator arm I43 which is operated by actuator coil I44 energized by the A. C. supply from terminals I45. The A. C. supply is rectified to form a series of pulses for operating the vibrator I43 by half wave rectifier I48. Thus the D. 0. signal is modulated at the frequency of the A. C. supply.

The elevator control amplifier receive its input through transformer I41 and comprises resistance coupled tubes I48, I49 and I50 an pushpuli output tubes III and I52. Its output is coupled to field coil I53 oi the elevator control motor by transformer I54. The other field coil I55 of the elevator control motor is energized by the A. 0. supply th'rough conductors I56 and Ill.

The operation of this amplifier is in all respects similar to that of the turn control amplifier, with the exception of the operation of the elevator control motor speed measuring bridge which includes field coll I53 and resistance I5l as one pair of. arms and inductance I50 and resistances I50 and iii as the other pair. In

order to prevent hunting of the aircraft about the cours defined by the glide path transmitter, the output from this speed measuring bridge is introduced into the elevator control amplifier at control grid I62 of tube I49. The function of this speed responsive signal is in all respects similar to that of the signal produced by the bank motor speed bridge, and it therefore prevents overrunning of the elevator control motor 45 and consequent hunting.

As described in connection with Fig. 2 the elevator control motor is operatively connected to the automatic pilot and by operation thereof controls the angle of climb or descent of the aircraft. 'Ih'e directional correction in the vertical plane caused by operation of the elevator control motor 40 is measured by the output from follow-up potentiometer 42 operated by the motor and the input to the elevator control amplifier becomes zero when this voltage is equal and opposite to the positional signal measuring the vertical departure from course. Th elevator motor speed measuring bridge is effective to prevent overrunning of the motor and hunting of the aircraft about the desired direction in the vertical plane.

In order to accomplish directional corrections proportional to the rate of change of departure in a vertical direction from course, I employ circuit components for superimposing on the positional signal a component proportional to its rate of change. These ar illustrated in Fig. 6, and for the purposes of illustration a diflerent circuit has 15 been shown from that employed with range receiver I for' controlling the heading of the aircraft.

The output from the glide path receiver is connected by conductors I and Ill to a bridge circuit comprising resistances ill and I" and mutually coupled inductances I and I". The output from the bridge circuit is supplied to terminals iii and in through conductors I'll and "I. It will be understood that in a steady-state condition induotances I" and ill eflectivcly shunt .the output received at terminals Ill and III,

but that they oppose a proportionately increasing resistance on a rising signal to increase the output relative to their action in a steady-state condition; and generate an opposing voltage on a decreasing signal to reduce the output relative to their action in a steady-state condition. The bridge therefore superimposes on the positional signal a component proportional to its rate of change, and the resulting signal supplied at terminals Iii and I3! causes .the elevator control motor to correct the direction of the plane in proportion to the rate of change of departur in the vertical relative to the course deflned by the glide path transmitter.

It will be understood that in landing the automatic vertical control of the aircraft should be immediately terminated on contact of the aircraft with the ground either automatically or by a manual control operable by the pilot. For this purpose switch I18 is provided in conductor ii! for deenergizing the fleld coil III of the elevator control motor 40.

In accordance with the above description it will be understood that the invention contemplates the completely automatic control of the flight of an aircraft in dependency on positional information derived from radio signals. Under operation of my system the aircraft is automatically guided to maintain the desired course. The system is similarly designed to automatically land an aircraft, which operation is automatically carried out without requiring any manual control dependent upon the personal Judgment of the pilot.

Whereas it is desirabl to employ the complete system, under certain circumstances only certain components thereof need be utilized. For instance, my turn control unit either with or without the bank control unit may b employed in instances where it is unnecessary to maintain an automatic control of the altitude of the aircraft. Similarly, the altitud control unit may be used alone, where automatic control of turn and bank of the aircraft is not desired. It is clear that the operating principles of my system are not restricted in any way to the speciflc circuits described, but may be utilized in other embodiments.

Divisible portions of the invention or inventions hereinbefore described have been made the subject of a later application constituting a continuation-in-part of the present application, Serial No. 444,395, flied May -25, 1942, for Radio controlled pilot system, and a divisional application Serial No. 505,917, flied October 12, 1943, for Radio controlled pilot system.

I claim:

1. In an aircraft flight control system, in combination, automatic pilot means for steering the aircraft in a desired direction, control means for the automatic pilot means operative to cause the automatic pilot to change the direction or the aircraft, means for deriving a control potential varied by the rate of change of departure of the aircraft from a desired path of travel, and actuating means for the automatic pilot control means operative in dependency on said control potential to turn the aircraft toward course by an angle depending at least in part on the rate or change of departure from course.

2. In an aircraft flight control system wherein a signal voltage proportional to the position of said aircraft relative to a predetermined flight path is produced, electromagnetic actuating means for causing operation of said steering control means, aircraft steering control means, a control circuit for said actuating means adapted to receive said signal for controlling the electromagnetic actuating means, means responsive to said signal voltage adapted to produce a component thereof proportional to the rate of change of said signal voltage, and circuit means connecting with the control circuit operative to superimpose on the signal voltage said component proportional to the rate of change of the signal voltage.

3. In an aircraft flight control system wherein a. signal voltage varying proportionally to displacement of said aircraft from a desired path of travel is produced, aircraft steering control means, electromagnetic actuating means for operating said aircraft steering control means, a control circuit for said actuating means adapted to receive said signal voltage, means responsive to said signal voltage adapted to produce a component thereof proportional to the rate of change of said signal voltage, and circuit means connecting with the control circuit operative to superimpose on the signal voltage said component proportional to the rate of change of the signal voltage.

4. An actuating device for controlling an aircraft automatic pilot to return the aircraft to a. desired flight path including electrical circuit means adapted to receive a positional signal from a radio receiver proportional to the departure of the aircraft from the desired flight path deflned by said signal, means responsive to the rate of change of the positional signal in said circuit, and actuating means for controlling said automatic pilot operating in dependency on the last mentioned means in response to the rate of change of the positional signal to cause the automatic pilot to turn the aircraft toward the desired course through an angle depending at least in part on the rate of departure of the aircraft from the desired flight path.

5. In a system for automatically steering a dirigible craft to follow a predetermined course deflned by radio signalling, means operable in response to said signalling, means controlled by said signal responsive means proportionally to the rate of change of position of said craft relative to said course, and means actuated at least in part by said last-named means connected to correct departures or said craft from said course.

6. In a flight control apparatus for automatically directing a craft along a predetermined path deflned by a radio signal, means at said craft responsive to said signal, steering controls on said craft, and means connecting said signal responsive means to actuate said steering controls to maintain said course by directional corrections proportional to the extent of departure from said course, said last-named means being responsive to the extent of departure of said craft from said course and to the rate of change of said departure.

7. In a flight control apparatus for automatically steering an aircraft along a predetermined course defined by radio signalling, means at said aircraft responsive to said signahheading control means on said aircraft, and means connecting said signal responsive means for actuating said heading control means to return said aircraft to course by directional corrections proportional to the extent of saidlateral departure and to the" rate of departure from said course.

8. In a control system for steering a craft relative to a course defined by a radio signal comprising two components of different characteristie on either side of said course. a receiver on said craft responsive to said signal and adapted to produce a dual alternating current output corresponding to said components, rectifying and mixing means comparing said dual output components to provide a direct current signal proportional in amplitude to the relative strengths of said components, means converting said direct current ignal to a proportional alternating current signal, means operative in response to a change in polarity of the direct current signal resulting from displacement of said craft to one side or the other of said course, to shift the phase of said converted signal, and motor means operated by said converted signal, said motor means being responsive to said phase shift for determining the direction of operation of said motor means.

9. In a control system for automatically steering an aircraft along an equal intensity path created by radio waves forming partially overlapping radiation patterns in space, automatic pilot means for stabilizing said aircraft on an adjustable heading, radio receiving means responsive to said radio wavesfor producing a control signal having an amplitude substantially proportional to the difference in intensity of said radiation patterns at said aircraft, and turn control means actuated by said receiving means for changing the heading of said aircraft by an angle proportional at least in part to theamplitude of said control signal to maintain said aircraft on said equal intensity path.

10. In a control system for automatically directing an aircraft along a predetermined line of flight defined by directively' radiated electromagnetic energy, automatic pilot means for stabilizing the longitudinal axis of said aircraft at an adjustable pitch angle, radio receiving means responsive to the intensity of said radiated energy for deriving a pitch signal having an amplitude which is a measure of displacement of said aircraft from said predetermined line of flight, and means responsive to said signal for changing said adjustable pitch angle by an angle dependent upon the amount of said displacement to direct' said aircraft back to said predetermined line of ht.

11. In a control system for automatically directing an aircraft along a predetermined line of flight defined by directively radiated electromagnetic energy, automatic pilot means for stabilizing the longitudinal axis of said aircraft at an adjustable pitch angle, radio receiving means responsive to the intensity of said radiated energy for deriving a pitch signal having an amplitude which is a measure of displacement of said aircraft from said predetermined line of flight, means for deriving a rate of pitch signal from said receiving means corresponding to the rate of displacement of said aircraft from said predetermined line of flight, and mean actuated 18 by said pitch and rate of pitch signals for changing said adjustable pitch angle by an angle dependent upon the magnitudes of said signals to direct said aircraft back to said predetermined line of flight.

12. In a control system for automatically steering an aircraft along an equal intensity path defined by partially verlapping radiation patterns, automatic pilot eans for stabilizing said aircraft on an adjustable heading, radio receiving means responsive to the relative intensities of said radiation patterns for developing a signal representative of lateral departure of said aircraft from said equal intensity path, and means responsive to said receiving means for'adjusting the heading of said aircraft through an angle dependent upon the magnitude of said lateral departure to return said aircraft to said equal intensity path.

13. In a control system for automatically steering an aircraft along an equal intensity path de-' flned by partially overlapping radiation patterns, automatic pilot means for stabilizing said aircraft on an adjustable heading, radio receiving means responsive to the relative intensities of said radiation patterns for developing a turn signal representative of lateral departure of said aircraft from said equal intensity path, means for deriving a rate of turn signal from said receiving mean representative of the rate of lateral departure of said aircraft from said equal intensity path, and turn control means actuated by said turn and rate of turn signals for adjusting the heading of said aircraft through an angle dependent upon the magnitude of said signals to return said aircraft to said equal intensity path.

14. In a control system for automatically directing an aircraft along a predetermined line of flight defined by directively radiated electromagnetic energy, automatic pilot means for stabilizing an axis of said aircraft, radio receiving means responsive to the intensity of said radiated energy for deriving a signal having an amplitude which is a measure of displacement of said aircraft from said predetermined line of flight, and means responsive to said receiving means for rotating said axis, through an angle dependent upon the amount of said displacement to direct said aircraft back to said predetermined line of flight.

15. In a control system for automatically steering an aircraft along an equal intensity path created by radio waves forming partially overlapping radiation patterns in space, automatic pilot means for gyroscopically stabilizing an axis of said aircraft, radio receiving means responsive to said radio waves for producing a control signal having an amplitude substantially proportional to the difference in intensity of said radiation patterns at said aircraft, and means responsive to said receiving means for rotating said axis through an angle dependent at least in part upon the amplitude of said control signal to maintain said aircraft on said equal intensity path.

16. In a control system for automatically steering an aircraft along an equal intensity path deflned by partially overlapping radiation patterns, automatic pilot meansfor stabilizing said aircraft on an adjustable heading, radio receiving means responsive to the relative intensities of said radiation patterns for developing a signal representative of lateral departure of said aircraft from said equal intensity path, means controlling the heading on which said aircraft is stabilized, and means for producing a signal dependent upon angular deviation of said aircraft from a predetermined heading, said control means being responsive to said signals for changing said aircraft heading an amount sufficient to balance said signals.

17. In a control system for automatically steering an aircraft along an equal intensity path created by radio waves forming partially overlapping radiation patterns in space, automatic pilot means for gyroscopically stabilizing said aircraft on an adjustable heading, radio receiving means responsive to said radio waves for producing a control signal having an amplitude substantially proportional to the difference in intensity of said radiation patterns at said aircraft, means controlling the heading on which said aircraft is stabilized, and means for producing a signal substantially proportional to angular deviation of said aircraft from a predetermined heading, said control means being responsive to said signals for changing said aircraft heading an amount suflicient to cause said signals to counteract each other.

18. In a control system for automtaically directing an aircraft along a predetermined line of flight defined by directively radiated electromagnetic energy, automatic pilot means for stabilizing the longitudinal axis of said aircraft at an adjustable pitch angle, radio receiving means responsive to the intensity of said radiated energy for deriving a pitch signal having an amplitude which is a measure of displacement of said alrcraft from said predetermined line of flight, control means for adjusting said pitch angle, and means for producing a signal substantially proportional to the degree of pitch of said aircraft from a predetermined pitch angle, said control means being re ponsive to said signals for changing said pitch angle an amount sufficient to cause said signals to counteract each other.

19. In a control system for automtaically directing an aircraft along a predetermined line of flight defined by directively radiated electromagnetic energy, automatic pilot mean for stabilizing an axis of said aircraft, radio receiving means responsive to the intensity of said radiated energy for deriving a displacement signal having an amplitude which is a measure of displacement of said aircraft from said predetermined line of flight, means for deriving a rate signal from said receiving means corresponding to the rate of displacement of said aircraft from said predetermined line of flight, and means actuated by said displacement and rate signals for rotating said axis of stabilization of said aircraft through an angle dependent upon the magnitude of said signals to direct said aircraft back to said predetermined line of flight.

20. In a control system for automatically directing an aircraft along a predetermined line or flight defined by directively radiated electromagnetic energy, automatic pilot means for stabilizing an axis of said aircraft at an adjustable angle, radio receiving means responsive to the intensity of said radiated energy for deriving a signal having an amplitude which is a measure of displacement of said aircraft from said predeof flight. control means for adthe and means for producing a signal subproportional to angular deviation of craft axis from a predetermined angle, trol means being responsive to said lilohanging said angle suillciently to cause tocounteracteaehother. asystemforsteeringadirigiblecraft an equal intensity path created by rawaves formin partially overlapping radiarng in space, radio receiving means reve to said waves for producing a displacet signal having an amplitude dependent upon difference in intensity of said radiation patat said craft, means for deriving a rate signal corresponding to the rate of change of said displacement signal, and utilization apparatus responsive to said displacement and rate signals for determining the corrective orientation of said craft required for restoring said craft to said path.

22. Apparatus for automatically navigating an aircraft having a turn control surface comprisingreceivermeansresponsivetoacourseradiation pattern including means for producing a reversible phase variable magnitude signal responsive to the relative position of the craft with respecttosaidcoursepattern andtotherateof change of said relative position, a control ampliiler, fed with said signal, a turn motor controlled from said amplifier, and automatic pilot means controlled from said turn motor, said au- -EEEE egg tomatic mean being connected for actuating the turn control surface of said aircraft.

, FRANCIS L. MOSH-HY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,958,259 Becker May 8, 1934 2,077,401 Crosby Apr. 20, 1937 2,165,800 Koch July 11. 1939 2,190,390 Thiry Feb. 13. 1940 1,818,708 Hammond Aug. 11, 1931 2,133,285 Dunmore Oct. 18, 1938 2,201,174 Harding et a1. May 21, 1940 1,942,567 Whitman Jan. 9, 1934 2,126,910 Moseley Aug. 16, 1938 2,163,411 Beeley June 20, 1939 2,253,508 Crane et al Aug. 26, 1941 2,266,410 Busignies Dec. 16, 1941 2,204290 Alkan June 11, 1940 2,137,974 l 'lschel Nov. 22, 1938 1,730,861 Nottage Oct. 8, 1929 2,315,386 Baldwin Mar, 30, 1943 2,209,826 Ogden July 30, 1940 1,339,930 Henderson May 11, 1920 1,061,191 Leonard May 6, 1913 1,804,126 Stoller May '5, 1931 1,586,233 Anschutz-Kaempfe May 25, 1926 2,300,742 Harrison et a1 Nov. 3, 1942 2,303,654 Newton Dec. 1, 1942 2,113,164 Williams Apr. 5, 1938 2,322,225 Crane et al. June 22, 1943 maleatwhichsaidaircraftissta Certificate of Correction Patent N 0. 2,423,336. July 1, 1947. FRANCIS L. MOSELEY It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows: Column 16, lines 12 and 13, claim 2, strike out thewords and comma steerin control means, and insert the same in line 11, same claim, after produced, and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 4th day of May, A. D. 194s.

THOMAS F. MURPHY,

Auiatmt flommmioner of Patents.

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